The verdict will allow generic drug makers within the country to continue selling cheap versions of the drug, which is used to treat chronic myeloid leukemia and other cancers. The BBCnotes that Novartis' drug costs $2,600, while generic versions of the drug cost just $175.

The court's decision is based on one specific part of India's patent law: section 3(d).

Here's how it reads:

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“It's all about interpretation of section 3(d) of the Indian Patent Act,” Ran Chakrabarti, a commercial lawyer based in New Delhi, told the Telegraph.

“Essentially, it says that you can't tweak something that already exists and then patent it, if it doesn't enhance the known efficacy of that thing, or result in a new product," he said.

The verdict may also even force drug companies to push for real innovations, rather than "evergreening" with minor improvements to keep the patent. Crucially, 3(d) calls for improved "efficiency" in requirements for a new patent — something can't just be new, it has to be better.

"Drug companies are going to have to come up with something pretty unique to get patent protection, and while that's good news for consumers, it pushes the threshold for innovation northwards." Chakrabarti told the Telegraph.

The ruling could set a precedent as a patents on a variety of other drugs are due to expire soon. In a statement about the ruling, Novartis makes clear that they feel this is Section 3(d) is an unfairly high hurdle:

Glivec has been awarded patents in nearly 40 other countries, including China, Russia and Taiwan, but the IPAB is denying one for India. The IPAB acknowledges that Glivec satisfies the international requirements for novelty and inventiveness, but it does not find Glivec to meet the requirement under Section 3(d) of the Indian Patents Act of 2005. This act introduced a new efficacy enhancement hurdle for patenting new forms of known compounds. We believe that Section 3(d), the Indian legal paragraph intended as a hurdle for evergreening, should not be applicable to the breakthrough medicine Glivec, which has changed the lives of patients with rare cancers.

India's generic drugs manufacturers are some of the largest in the world, thanks to laws that used to allow patents only for drug manufacture processes, not the final product, allowing companies to reverse-engineer many drugs.